Monitoring Building Instability by Sentinel-1 PS-InSAR:A Case Study in Taipei, Taiwan

Abstract: The improvement of spaceborne Synthetic Aperture Radar Interferometry (InSAR) technology has recently accelerated advancements and innovations in geological and engineering fields. One of the time series analysis techniques, PS-InSAR, utilizes persistent scatterers (PS) with stable phase information from SAR images over time and monitors surface deformation with millimeter accuracy. In this study, we aim to conduct PSInSAR in the Dazhi District of Taipei, where a major part was the old Keelung River, and a segment of the river channel was cut off in the 1990s. Owing to its geological characteristics and persistent compaction, this district has experienced land subsidence, posing a threat to residential buildings. A recent occurrence of damages in a district building has garnered public attention to the safety of structures, leading to increased calls for investigating the viability of satellite monitoring. We intend to use ESAs Sentinel-1 and apply PS-InSAR at the pixel level to measure the structures subtle motion in 20182023.In our preliminary test from a corner reflector set on the top of a building, the accuracy of pixel-wise detection of line-of-sight motion achieves ~1 cm level. The deformation in the neighboring area of the damaged building is shown, while an accelerated sinking velocity has been noted since early 2023. It may provide a case study to discern potential collapse beforehand and set warning criteria. Key Words: Persistent Scatterer InSAR, Sentinel-1, Building collapse, Deformation